I decided to build my own LED (light emitting diode) grow light since i didn't want the pre-build led light because it favors red over blue wavelengths.I will split this post into 2, first some theory about LEDs in general, growth leds, and some physics 101 that is of interrest when building your own led light.

Light emitting diodes:The principal leds depends on electroluminescence, which means light through electricity and was first discovered in 1907.The whole principal in a nutshell is, electrons are excited to a higher orbit and releasing light when going back to the ground state.The Color of the led depends on the level the electron is excited to, lesser orbit means a higher wavelength (energy is a to the power -1 function of wavelength), the materials used in leds to create different colors are:(GaSb), GaAs, indium phosphide (InP), and silicon-germanium (SiGe)Reason LEDS are becoming more common is that they are way more energy efficient then an incandescent or fluorescent light because of the required energy less is transferred to heat, and more into light (which is also heat but another wavelength which we consider useful)

Growth LEDS:The earliest lifeforms on earth could not produce their own energy, but gladly they evolved.The first plants that used photosynthesis to produce energy were cyanobacteria and eventually they evolved further, and somewhere between a few milion years ago and now, carnivorous plants became to exist.Every plant uses photosynthesis, which is: using light to make usable energy.Plants do this by capturing electrons (light) by having chlorophyll. The 2 main chlorophylls in plants are Chlorophyll a and chlorophyll b.

In these chloroplasts there are Photosystems (I and II), which can "capture" electrons and divert them to make all kind of molecules (like making O2 from CO2 and ATP => making energy aka photosynthesis)But the rate at which plants can use electrons is depending on the wavelength (also commonly known as color):Therefore it can be concluded that giving plants the light they can use most efficiently (most usable electrons per watt of energy) is the light at the maximum absorption.So became the LED grow lights.

I have to say i have found very few commercial grow lights that consider these peaks (they come close but as u can see a 20nm change can mean 60% less efficiency), that's one of the reasons i made my own.Another reason is that comercial lights favored red, and i wanted more vegetative growth (which comes from blue light) instead of potgrowers which want flowering (achieved from red light).

First i decided on which leds to use and which power supply, then calculated which leds could be grouped together (voltage wise), the 420-450 and 6000k leds were similar in voltage 4.0-4.2 V.

Plan of the build:Then i started drawing up -a more or less- evenly disributed array of leds, aiming for ~50 watts in power usage, done this a few times, determining what was the best way soldering and led distribution wise. the final design is as follwing:(-)420-450-6500(+) (+)420-450-6500(-) (-)660-660-660-660-660(+) (-)6500-450-420(+) (+)6500-450-420(-) (-)630-630-630-630-630(+) (-)420-450-6500(+) (+)420-450-6500(-) (-)660-660-660-660-660(+) (-)6500-450-420(+) (+)6500-450-420(-) (-)630-630-630-630-630(+) Where the (+) means positive, and (-) negative, this way i have most of the positive wires in the middle and negatives on the outside, easier wiring this way with ~50 leds.

When not glued yet, use the thermal glue to glue the individual leds to a star heatsink

Glue them to your heatsink (in my case an aluminium plate)

O wait, i needed a layout

finally done, glueing the leds and soldering the wires in between (the 420-450 and 6000k leds were in sets of 3, the 660 and 630 leds in sets of 5 (due to difference in voltage), ceramic resistors were soldered into each set.

Video:

This is the complete panel except 5 660nm leds, so actual intensity will be higher, as a reference, full sun is 1800 microEinstein, 2x6500k 18w t8's measured 250 mE at 20 cms away.

Due to high energy prices here (~25 eurocents per kWh) i cut the whole in half so i ended up with 3-3-3-5-5 ratio of 420-450-6000k white-630-660 nm led, these are my helis under them at about 20-30 cms away with the single 22w lamp covering an area of 40x80 cm's:

This setup is cooled by a 8 cm diameter fan, and the aluminium plate i used as "board" only gets about 10 degrees above ambient temperature.

So in all, leds, and especially well designed leds can be a very good subsitute for CFL's when it comes to growing cp's, yet there are a lot of unknowns and research needs to be done in order to truely understand the effects of differences in wavelength on cp growth.

Please feel free to ask questions regarding grow LED's and i will do my best to find the answer!

Last edited by Sander on Mon May 05, 2014 10:14 am, edited 12 times in total.

Well Ae9803, i had 20 leds on a 20x16cm aluminium board, which was already 20 degrees above ambient temperature, and i added about 20-25 more on the same plate, so i recon the temperature would be at least 50 degrees C above ambient temperature, so it does heat up a fair amount, but not as much as a indecent bulb

Hey mikey, thx!No, not yet, if i wanted something it would be a mantis shrimp!Well, im about to do some *tests* this autumn and winter if i can get a decent sample size, so ill update it sometime (i know, still have lots to do)

Could you add some captions to the photos when you are less busy? I know pretty well what's going on here, but I'd still like a little narrative to get an idea of your workflow/attack strategy.

Are you going to add more "fins" or aluminum to the heat sink? Or just the fan?

I added some of the captions, yet there kinda random.Also, an explanation of the build process has been added, if u need more help with the electrical part (voltages, resistors etc) let me know.And no fins or anything were needed in the end.

What is the recommended and above average of wattage to use to avoid burning the plants? I have this sliding type of door http://caldwells.com/sliding-closet-door-hardware and plan to put the pot and covers every side of above sliding portions. Need some guides that will help me on every aspect..